Studies on Influence of Nanoparticle Capping Agent on the Response of Palladium Based Resistive Hydrogen Sensors

Abstract

Palladium NPs were synthesized by the polyol reduction technique. These NPs havebeen studied for hydrogen gas sensing. The stabilizer [Polyvinyl pyrrolidone (PVP)] concentration, which is a synthesis parameter, was optimized with respect to the hydrogen gas response. It has been verified that the sensing performance was tunedby modifying this synthesis parameters. This is due to the shape and size attributesof nanoparticles which are function of this synthesis parameter. In this work, effortshave been made to correlate hydrogen gas sensing with PVP concentration (the chosensynthesis parameter). Nano palladium was characterized by HRTEM, GIXRD,and UV-Vis spectroscopy. Typical sensing mechanisms were formulated to visualizethe sensing phenomenon.HRTEM study showed that the palladium nanoparticle shape and size were dependenton stabilizer PVP. Different shapes viz., nearly spherical, octahedron, etc., wereobtained in this study. Hydrogen response pattern of these NPs near room temperaturewere correlated to the variation of the concentration of PVP. It was observedthat the size distribution in palladium nanoparticle influenced the hydrogen sensitivity.The sensing was analysed with respect to the variation of NP size and size newlinedispersity. The size modulation by PVP was verified by UV-Vis data where peakshift was observed with the increase in PVP. The H2 response at elevated temperaturewas also studied.Parametric study based on washing of NPs was done for understanding hydrogengas sensor performance. It has been found that water washed palladium nanoparticlesshowed intense hydrogen response than ethanol washed nanoparticles. Thestrain data (from GIXRD) revealed that the water washed devices have more strainin the Pd atoms than ethanol washed Pd NPs; such difference in strain may assistthe geometric response during hydrogen sensing. The negligible catalytic contamination newlineof the sensing material was analyzed with XRD data. Furthermore, long termvalidity was proved by testing the devices for a period of 8-9 days regularly. In fact,reproducible behaviour was observed after one month of testing. newline newline